The invention relates to a spice grinder that can be screwed onto a jar containing a spice, where the jar has at least one outward projection that interacts in such a way with an inward projection or a part of the spice grinder that is to be screwed onto the jar so as to block any reverse rotation after the two projections have moved past each other as the spice grinder is screwed onto the jar.
It is frequently desirable or even necessary to close a container provided with a screw-type closure in such a way that the container can no longer be opened by turning the screw-type closure in the reverse direction. In this manner, inadvertent removal of the cap and spilling the contents is avoided. This is also true of glass spice containers onto which a spice grinder, typically of plastic, can be installed. These units involving a jar with a spice grinder built into the cap are disposable items, not intended for refilling.
Approaches have already been proposed for preventing the spice grinder from being unscrewed from the jar. These spice grinders have the features described above. For instance, US 2012/0286081 proposes providing complementary ramp or sawtooth shaped structures on the cap and on the jar, with their shallow and steep flanks oriented oppositely. The cap can be screwed on the shallow flanks of the formations meeting and sliding over one another with elastic deformation of the cap and/or jar when the cap is first screwed onto the jar. Once screwed on, reverse rotation of the cap on the jar will cause the two steep flanks to angularly flatly abut each other, thereby blocking removal of the cap.
Instead of the two ramp formation, U.S. Pat. No. 4,669,624 proposes one ramp formation coacting with another radially projecting ridge of uniform radial height. Similarly, EP 0,571,780 proposes ramp-shaped formations on one of the screwthreads that cuts into the material of the other part and inhibits reverse rotation. The functioning is similar.
The problem with these systems is that substantial deformation of the jar neck and/or cap is necessary to screw the cap onto the jar. The deformation can damage the parts and also makes assembly of the product difficult.
Further, with this system the locking is not very strong. The ramps are designed for easy assembly, so that a hard reverse turn can overcome the ramps and unscrew the cap. Since the spice grinder is meant to be used by all types of people, a particularly strong person who reverse-turns the cap can damage the latch and free the cap. Furthermore, on small bottles, it is impossible to provide sufficiently large formations to adequately resist reverse rotation. On the other hand, large-mouth jars cannot be made flexible enough for the system to work effectively and typically require considerable torque to get the cap properly screwed onto the jar. The problem with large jars is that they must be gripped with considerable radially inwardly effective force, directly counter to the outward radial deflection needed to allow the ramps to pass each other, especially when the jar is of glass with no meaningful elasticity.